If you've been using dual-channel motherboards, then you've become accustomed to having the (nearly) full 4GB memory address available. With X58 you're limited to 3GB, which is further reduced by any other memory (video/audio/etc) that may amount to more than 1GB.

In dual channel with 4GB RAM + 1GB GPU your OS would give 3GB RAM to the CPU and 1GB to GPU which leaves 1GB of RAM unusable. A triple channel system having 3GB RAM + 1GB GPU would actually be right on spot with the 4GB OS barrier. So obviously, not only your logic is flawed but your basic math is also wrong.I don't see how it is different to have 4GB RAM + 1GB GPU or 3GB RAM + 1GB GPU. In the end your CPU will only address 4GB memory so in the dual channel config you are wasting 1GB. Assuming a 2GB GPU in dual channel configs you will get 4GB RAM + 2GB GPU= 2GB RAM + 2GB GPU which means you will waste 2Gb of RAM (assuming the OS will keep favouring GPU memory over RAM). In triple channel you would get 3GB RAM + 2GB GPU = 2GB RAM + 2GB GPU.If the OS decides to cut off the extra 1GB from the GPU then you still end up with 3GB RAM and 1GB GPU in both configs.Not a con.

Why would someone that buys a $300+ mobo run a. 3gb of ram or b. a 32bit os. I see no reason to even bring up something so trivial, especially as a 'con'. Also "BIOS options can be complicated for some users", if you buy this board, again someone spending $300+ on a high-end board probably knows what they're doing.

Just because you might personally know and understand that only 64-bit Operating Systems will support anything more than 4GB of system memory, doesn't mean that everyone else does... including people who have bought this enthusiast motherboard. Just take look at some of the feedback left at the retailer websites for proof.

My rating is subjective, and it is my own. As I say at the beginning of the Conclusion page: Please do not base your purchases solely on our conclusion.

Be aware that page 2-11 of the P6X58D Premium User Manual says "Due to Intel spec definition, X.M.P.DIMMs and DDR3-1600 are supported for one DIMM per channel only." That means higher speed memory is only supported for 3 DIMMs, leaving 3 memory slots empty. Be cautious if you plan to use 24 GB of system memory at the higher speeds. Searching the web for success/failure stories is advised.

Excellent review, but I noticed a possible error. You stated that 6 of 32 PCIe lanes are borrowed from graphics for USB 3.0/SATA-6G support. However, Intel?s X58 IOH supports 36 PCIe lanes, of which 32 are required for 16x/8x/8x triple-SLI/CFX. I?m not sure why the motherboard would reserve six lanes, since only four are used by the ASUS U3S6 PCI-E 4x expansion card. It appears that the graphics performance of this motherboard may not be crippled after all. Although I?m still not sure what happens in the 16x/16x/1x configuration, since an extra lane is required.

The memory controller is integrated on LGA1366 CPU's, like the LGA1156 CPU's, though the latter seem to have more aggressively optimized memory controllers (perhaps being dual channel they can be optimized more than a triple channel controller?).

The X58 IOH has: 36 PCIe lanes, 4 PCIe lanes linking to the ICH10 southbridge, and a QPI link to the CPU. Unless ASUS are insane, the SATA3 and USB3 controllers would use 4 PCIe lanes from the IOH, leaving a full 32 PCIe lanes for graphics (16 + 16, or 16 + 8 + 8). The PCIe 1X slot, the 1X lane for 16 + 16 + 1 mode, and PCIe lanes for the gigabit LAN would be provided by the ICH10.

This P6X58D runs cool 39-45cent with 7-7-7-20 Patriot pc10666,3x2gb.My evga 141-BL-E757-TR run 60cent but it is great to leran to adjust cpu. I let speedstep in Advance Menu(bios) use my operating sytem to run the o/c.

#1. It's not a memory limit, but an address space limit. System memory+Sound Card+Video Card+NIC+Etc all have share this 4GB memory space.#2. Windows client(Non server variants), use to support PAE for memory reasons, but drivers ALSO need to correctly support the feature otherwise memory/data corruption can happen. MS decided too many companies couldn't make decent drivers and disabled extended memory for non-server versions.#3. Who uses 32bit OS's anymore? That's like using dial up when you have access to FIOS.

(1) Does the fact that both the ASUS and Gigabyte motherboards are designed so SATA-III borrows from PCI-E link lanes mean that I am not going to get the benefit of SATA-III ?

(2) Am I correct to assume that the ASUS motherboard will not support SATA-III Raid 0 ?

(3) Which gives the most bang-for-the-buck: the Crucial RealSSD-C300 with a SATA-III controller (the Marvell SE128 on the Gigabyte motherboard), or the Intel SSD 80GB with a SATA-II controller (the Marvell SE123 on the ASUS motherboard) ?

(4) And finally, if I go with the Gigabyte board, I am thinking about going with the Gigabyte GA-X58A-UD5 as opposed to the ?UD7... as I am an architect using CAD and GIS and not a gamer and thus don?t see the need for advanced cooling. Any problems with this decision ?

1) SATA-6G (aka SATA-III) is limited to 5.0 GB/s for motherboards using a controller on the PCIe bus. Presently there isn't an SSD that comes close to that limit, and HDDs barely touch SATA-3G. You'll need a SATA-6G drive that produces more than 300MB/s to make it worth the while.

2) You are correct.

3) Crucial is faster for sure, but I think the OCZ Agility or Corsair Nova are the best bang for the buck.

4) I would use P55 and not X58. My company has built many CAD/CAM systems, and you want to spend your money on a very fast HDD or SSD, decent video card, and plenty of RAM. P55 does a better job with memory and CPU performance than X58... clock for clock.

After reading this review i would agree that the 3 gb barrier is no fault of the mainboard but a limitation of 32 bit o/s, they should of tested it on 64 bit o/s as i run win 7 64 myself and its fantastic on one of these boards with 6gb ddr3 1866 & i7920 clocked to a modest 3.5 ghz, runs everything very quickly, have even had my processor up to 4.2 ghz with no problems but the 920 requires a lot of voltage for that to be stable, the only flaw i can see is the 2 pcie X16 slots are too close for 2 dual slot cards to be ran other than that its a great solution in my opinion

So you read this article, but didn't see our Test Methodology section that clearly states we used Windows-7 Ultimate Edition 64-Bit? Oh, and it's a 4GB barrier, not 3GB; although our test system used 6GB DDR3.